volunteer receives SMS reminder to submit court report

[Zrrrpy]

Part of epic #1017, dependent on #1785, #1791, #1780, #1781, #1782, #1783

AS a volunteer,
I WANT to receive an SMS notification reminding me to submit a court report,
SO THAT I submit it in a timely manner to my supervisor and they have time to review it before my court appearance.

How it works now

This reminder currently only sends via email. (See #620)

How it should work

IF volunteer is assigned to at least one casa_case with an upcoming court date and a corresponding court report due date,
AND it is seven calendar days before the court report due date,
AND court_report_submitted=false,
AND volunteer is opted into receiving text messages,
THEN volunteer receives SMS reminder to submit court report.

Acceptance Criteria

• when the above criteria are met (outlined beneath "How it should work"), volunteer receives SMS reminder
• SMS reminder reads something like this, depending on character restrictions:
  Your court report is due on [court_report_due_date]. Generate a court report to complete & submit here: [link to generate court report]
• The volunteer cannot deactivate this SMS notification

[github-actions]

This issue has been open without changes for a long time! What's up?